1. Field of the Invention
This invention relates to mark reading systems used in obtaining information from groups of people by having the individuals (respondents) fill in pre-printed forms by placing marks in selected boxes on the forms which are then scanned and analyzed by optical mark reading (OMR) equipment. More particularly, this invention relates to techniques for generating the pre-printed forms more easily and economically than heretofore, and for automatically reading such forms more reliably than heretofore.
2. Description of the Prior Art
Pre-printed mark read documents have been used for many years, for example, in the form of answer sheets for multiple-choice tests for students. Conventionally, the completed answer sheets are processed by automatic test scoring devices including optical mark reading apparatus.
Typically, the pre-printed forms carry alphanumeric characters together with associated boxes in selected ones of which the respondent will insert marks, to indicate his response. A stack of completed forms can be processed rapidly by optical sensing equipment. A computer associated with the scanner carries out a program to determine the responses selected by each person and to compile a summary or other analysis of the results.
One of the problems with such mark read systems is that preparation of the pre-printed sheets is undesirably costly. Another problem with such systems is that too many sheets are rejected during automatic processing due to failure of forms to meet specifications in spite of costly preparation.
Present systems in use today ordinarily print the boxes in drop-out ink, i.e. ink that is (for the particular scanning beam wavelength) not reflectively (or transmissively) different from the background of the sheet, and that therefore will not be "seen" by the optical scanning beam. Reference may be made to U.S. Pat. No. 4,217,487 and Re 29,104 for further information on such drop-out inks. In such systems, the boxes are seen visually by the person filling out the form, but the optical scanning apparatus does not "see" the box and simply examines the region of the document where it is instructed to look for a mark.
The regions to be examined for marks in such prior art systems are identified to the OMR equipment by external controls which may differ from system to system. One common approach makes use of so-called timing marks which are pre-printed at intervals down one side edge of the document. See, for example, U.S. Pat. No. 3,900,961. Through the scanning of such timing marks, the scanner determines in accordance with pre-set instructions where to look for a possible mark inserted by a person filling out the form, and makes a record of each mark so found.
It is known that certain difficult-to-control variables can cause unsatisfactory operation of such a system. For example, the drop-out ink printing on the document can be out of registration, causing the respondent and the optical mark reader (OMR) to be looking at two different locations for (1) placement and (2) detection of a mark. That is, the OMR equipment will, in such case, examine a region different from that identified by the printed box. Errors can be so large in some instances as to completely miss the mark or pick up a mark from an adjacent box. Printing the documents to tighter tolerances can improve performance, but is still more costly.